Building a New Computer: 32-bit or 64-bit? Intel or AMD?

I currently have an ASUS P4P800 Motherboard, 2 GBs of RAM, and an Intel 2.8GHz HT CPU overclocked to 3.36GHz; it's about two years old now and is still faster than most computers. I plan on making this computer a linux box on my router's DMZ. So, I want another desktop.

I know 64-bit is starting to pick up, but it is extremely expensive. Is Windows' Vista going to support 32-bit and 64-bit processing? Are all new factory computers going to be 64-bit in the near future? If I stay with a 32-bit motherboard and CPU, am I going to regret it in year?

Of the new Intel processors, I believe D and EE are 64-bit, correct? So, I would need a 64-bit compatible motherboard. I've never dealt with AMD chipsets, but I hear they starting to get more "powerful" than Intel chipsets. Should I go with Intel or AMD?

As you can probably tell, I'm very lost on what to do and what kind of CPU & MB to put in my new system. I am not gamer, but I do a lot of multi-tasking and like having a powerful computer. Any information or recommendations on what kind of CPU & MB to buy would be greatly appreciated... as well as the pros/cons of taking a 32-bit route versus a 64-bit route.

I want to build the new computer for around $1000-$1200, but I know this probably possible if I take the 64-bit route. Am I better off waiting for another 6 months or so to see where 64-bit technology is headed (and the prices of 64-bit CPU dropping)? Or should I just go ahead and build a sweet 32-bit system? I want to build a desktop, like my current one, that will still be extremely fast for years to come. Thanks!